Numeric controller

ABSTRACT

The chopping control process is allowed without adding the chopping dedicated axis. To correct the chopping operation for a movement error in the contour control with the positioning axis or rotation axis, an interpolation processing part  12  and an axis control processing part  13  are provided with a function of generating the movement data for making chopping operation by controlling two or more axes at the same time and a function of correcting the chopping operation.

TECHNICAL FIELD

The present invention relates to a numerical control apparatus, and moreparticularly to a so-called chopping control for controlling theoperation with the reciprocating movement in any direction at any periodand amplitude in accordance with a commanded processing pulse.

BACKGROUND ART

The conventional numerical control apparatus involved makingindividually a contour control in the X-Y axis direction and a choppingcontrol for effecting the reciprocating movement at any period andamplitude.

Therefore, when the chopping control process was performed in thereciprocating movement at any period and amplitude in accordance with acommanded pulse, using the numerical control apparatus, a machine tool(e.g., grinding machine) controlled by this numerical control apparatusadditionally had a chopping dedicated axis (chopping axis), other thanthe normal control axis (X axis, Y axis and so on).

When this machine tool is employed under the chopping control of thenumerical control apparatus, the necessary information for the choppingoperation, such as the amplitude (positions of top dead point and bottomdead point) and the reciprocating movement period necessary for thechopping control, are set in advance as the parameters. Then, thechopping axis (e.g., about which the grinding stone is operated) ispositioned vertically along the Z axis for the contour locus on the X-Yplane (horizontal plane), and reciprocated in the Z axis direction, inwhich a table with the workpiece laid is moved in the X-Y axis directionalong the control axis to make the contour control, so that the choppingcontrol process is performed with the contour commanded in theprocessing program, as shown in FIG. 10.

Also, when the chopping control process was performed in a state wherethe processing face of the workpiece was inclined, as shown in FIG. 11,using the numerical control device, the machine tool was provided with arotatable chopping axis for making the chopping operation in the statewhere the workpiece was inclined at a predetermined angle and a rotationaxis (C axis) around which the grinding stone was rotatedperpendicularly to the processing face on a mechanism for moving thegrinding stone along the control axis in the X-Y axis direction.

The machine tool as shown in FIG. 11 performs the chopping controlprocess by making the reciprocating operation and rotational operationfor the workpiece (chopping axis) in the arrow direction in the statewhere the workpiece is inclined, as well as causing the grinding stoneheld perpendicular to the processing face by rotating the rotation axis(C axis) to be moved in the arrow direction by adjusting the controlaxis in the X-Y axis direction.

By the way, the conventional numerical control apparatus performedindividually the contour control in the X-Y axis direction and thechopping control for making the reciprocating operation in any directionat any period and amplitude, as described above. Therefore, the machinetool with the conventional numerical control apparatus capable of thechopping control process required a dedicated chopping axis forrealizing the chopping operation in the reciprocating movement,separately from the control axis for contour control.

Also, in the machine tool with the numerical control apparatus forrealizing the chopping operation in any oblique direction as shown inFIG. 11, the rotation axis (C axis) for rotating the toolperpendicularly to the processing face was required, other than thededicated chopping axis.

In this connection, in the machine tool with the numerical controlapparatus capable of the chopping control process, the machineconstitution having the chopping axis mounted on a group of contourcontrol axes is required, resulting in a problem with the adjustment ormaintenance for the complicate mechanical constitution.

Also, in the machine tool for realizing the chopping operation in anyoblique direction as shown in FIG. 11, the rotation axis (C axis) isfurther required other than the chopping axis. Hence, various problemsarise with the manufacturing cost and superposition in the mechanicalaspect, as compared with the machine as shown in FIG. 10.

Moreover, since it is permitted to correct the chopping operation for anerror (e.g., when the period is faster, the actual amplitude is shorterthan the predefined amplitude due to a delay of servo control) only withthe chopping axis, there was a problem on the control that it wasdifficult to correct the chopping operation for a movement error in thecontour control with the positioning axis or rotation axis.

DISCLOSURE OF THE INVENTION

The present invention has been achieved to solve the above-mentionedproblems, and it is an object of the invention to provide a numericalcontrol apparatus in which the machine tool making the chopping controlprocess does not require the dedicated chopping axis.

Also, it is another object of the invention to provide a numericalcontrol apparatus that can correct the chopping operation for a movementerror in the contour control with the positioning axis or rotation axis.

In order to accomplish the above object, a numerical control apparatusof the invention comprises chopping movement data generating means forgenerating the movement data for making the chopping operation bycontrolling the two or more control axes at the same time.

Therefore, the machine tool making the chopping control process does notneed the dedicated chopping axis.

Also, a numerical control apparatus of the invention comprises choppingmovement data generating means for generating the movement data formaking the chopping operation by controlling two or more control axes atthe same time while making the contour control.

Also, in this invention, the chopping movement data generating meansgenerates the movement data for making the chopping operation for thecontrol axes at the same time while making the contour control in such amanner as to convolute the movement data for making the choppingoperation and the movement data for making the contour control, anddistribute the convoluted data to each of the control axes.

Therefore, the machine tool making the chopping control process does notneed the dedicated chopping axis, and the chopping control is easilyadapted to the shape of workpiece and the processing conditions.

Also, the numerical control apparatus of the invention further comprisescorrection means for correcting a servo delay of each control axis tomake the chopping operation at the same time while making the contourcontrol.

Also, in this invention, the correction means corrects a servo delay ofeach of two or more control axes to make the chopping operation at thesame time while making the contour control in such a manner as toacquire a servo delay amount of each control axis by comparing theactual position feedback information for each control axis making thechopping operation at the same time while making the contour controlwith a command value, synthesize the acquired servo delay amount of eachcontrol axis, and distribute the synthesized servo delay amount to achopping interpolation vector and a contour control interpolationvector.

Therefore, it is possible to correct the chopping operation for amovement error in the contour control with the positioning axis orrotation axis, and make the chopping operation at high precision.

Also, in this invention, a chopping operation initiation command and achopping operation stop command are issued from any one of a processingprogram and a ladder portion.

Therefore, the chopping operation initiation command and the choppingoperation stop command are issued from any one of the processing programand the ladder portion, whereby the chopping control initiation or stopis easily made.

Also, in this invention, various data regarding the chopping operationcommand are set as the parameters in a memory, and when the choppingoperation initiation command is issued, the chopping control isperformed using various data regarding the chopping operation commandset as the parameters.

Therefore, when the chopping operation command is issued from theprocessing program, it is only necessary to describe a choppinginitiation command code, whereby the processing program is simplified.Also, various data regarding the chopping operation command areappropriated for some other processing, and various data regarding thechopping operation command are easily modified, whereby the preparationtime before processing is shortened.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a numerical control apparatus according toan embodiment 1 of the present invention.

FIG. 2 is a detailed block diagram of the essence of FIG. 1 according tothe embodiment 1 of the invention.

FIG. 3 is a view showing an example of oblique chopping operationaccording to the embodiment 1 of the invention.

FIGS. 4(a) and 4(b) are views showing an interpolation process foroblique chopping in an interpolation part according to the embodiment 1of the invention.

FIGS. 5(a) and 5(b) are views showing an acceleration or decelerationprocess for oblique chopping in an acceleration or decelerationprocessing part according to the embodiment 1 of the invention.

FIGS. 6(a) and 6(b) are views showing the convolution of interpolationdata and the axis control in the oblique chopping according to theembodiment 1 of the invention.

FIG. 7 is a diagram showing an error quantity calculation in the obliquechopping according to the embodiment 1 of the invention.

FIGS. 8(a) and 8(b) are views showing a method for dividing an errorquantity in the oblique chopping into a chopping error component and acontour control error component according to the embodiment 1 of theinvention.

FIG. 9 is a diagram for explaining an error correction in the obliquechopping according to the embodiment 1 of the invention.

FIG. 10 is a view showing the conventional chopping control process.

FIG. 11 is a view showing another conventional chopping control process(chopping control process in the oblique direction).

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1

Referring to FIGS. 1 to 9, an embodiment 1 of the present invention willbe described below.

In this embodiment 1, the chopping control process is performed in astate where a processing face of the workpiece is inclined, as shown inFIG. 11.

FIG. 1 is a block diagram of a numerical control apparatus, and FIG. 2is a detailed block diagram of the essence of FIG. 1. In the figures, aprocessing program 24 or the setting data such as parameters input froman external input/output unit 23 via a man machine interface (MMI) 2such as a display device or a keyboard is stored in a program memory 4or a setting data holding memory 18 by an input/output data processingpart 3 or a communication processing part 7. The parameters include theinformation related with the oblique chopping operation controlaccording to the embodiment 1 of the invention.

The processing program 24 stored in the memory 4 or directly input fromthe external input/output unit 23 is analyzed by a processing programanalysis processing part 5.

At this time, when a movement command is issued, an interpolationprocessing is performed in an interpolation processing part 12, thecreated axial control data being sent to an axial control processingpart 13.

The axial control processing part 13 passes the axial control data to aservo amplifier 19 and a principal axis amplifier 20.

As shown in FIG. 2, the interpolation processing part 12 has a choppingoperation interpolation preprocessing part 121, a contour controlinterpolation controlling part 122, a chopping dedicated buffer 123 anda contour control dedicated buffer 124. The axial control processingpart 13 has an acceleration/deceleration controlling part 130, an errorcorrection controlling part 131 and an axial controlling part 132. Thedetailed operation of the interpolation processing part 12 and the axialcontrol processing part 13 will be described later with reference toFIGS. 2 to 9. Also, the interpolation processing part 12 and the axialcontrol processing part 13 constitute chopping movement data creatingmeans and correcting means as referred to in this invention.

The servo amplifier 19 and the principal axis amplifier 20 control aservo motor 21 and a spindle motor 22 connected in accordance with thereceived axial control data contents.

Also, in the case where data processed in the processing programanalysis processing part 5 is an auxiliary command (M command), the datais passed to a machine control processing part 10 to control a machine(ATC control, coolant ON/OFF) under the action of a ladder processingpart 9, a PLC interface 8 and a DI/DO controlling part (digitalinput/output controlling part) 11.

The numerical control apparatus can perform the NC control in accordancewith the outside signals input from an input/output controlling part 11and a built-in ladder program 31, in addition to the NC controlperformed by the processing program 24 input from the externalinput/output unit 23 via the man machine interface (MMI) 2 such as anordinary display device or keyboard as described above. In this case,the NC control is performed by calling the processing program held inthe memory 4 through the machine control processing part 10 or upon acommand directly issued to the interpolation processing part 12, basedon the result processed by the ladder processing part 9 via the PLCinterface 8.

By the way, the oblique chopping control is decomposed into the contourcontrol and the chopping in the operation, as shown in FIG. 3. Also, theoperation includes a component of convoluting the contour control on thechopping operation and a component of reciprocating obliquely atarbitrary angle in a rectangular coordinate system as a result, becausethe chopping operation of reciprocating at a fixed angle to a contourcontrol vector follows variations of the contour control vector.

Therefore, when the decomposed contour control is given a locus and aspeed, the chopping control is given at least angle A (angle relative tothe vector for contour control), amplitude R and frequency F, and theangle between the vector for contour control and the rectangularcoordinates is defined as angle B, synthesizing data, the obliquechopping operation at angle A+B with respect to the rectangularcoordinates X-Y.

Hence, the chopping control is enabled only with the control axes of Xaxis and Y axis originally possessed without adding the choppingdedicated axis to the machine tool.

Referring to FIGS. 2 to 9, the details of the constitution and operationfor realizing the chopping operation in oblique direction will bedescribed.

The numerical control apparatus 1 of FIG. 2 is a detailed block diagramin which a relevant portion of the embodiment 1 is excerpted from ablock diagram of the numerical control apparatus of FIG. 1.

That is, when the processing program analysis processing part 5 readsand analyzes a contour control command such as G01, G02 from theprocessing program, various values (block movement start coordinates,end coordinates, speed, acceleration/deceleration pattern and movementlocus shape, etc.) regarding the contour control command are passed tothe contour control interpolation processing part 122 of theinterpolation processing part 12, as shown in FIG. 2. Also, when theprocessing program analysis processing part 5 reads and analyzes achopping initiation command or a stop command regarding the choppingoperation from the processing program, various values (amplitude,frequency, correction amount for a servo delay in the reciprocatingoperation) regarding the command are passed to the chopping operationinterpolation preprocessing part 121 of the interpolation processingpart 12.

The chopping initiation command is given in the processing program inthe following format, for example,

-   -   G . . . R . . . A . . . F . . . Q . . . : ( . . . : any        numerical value)

Where G . . . is a chopping initiation command code, R is amplitude, Ais an angle of chopping operation for the movement vector in the contourcontrol, F is a frequency that is the speed of the chopping operation, Pis a correction amount measuring method, and Q is a correction amountstoring location. Also, the amplitude R, angle A and frequency F commandthe amplitude R, angle A and frequency F of FIG. 3.

Also, the chopping stop command is given in the following format, forexample,

-   -   GΔΔ (ΔΔ: any numerical value)

Also, a contour control command is given in the same manner asconventionally.

The chopping operation interpolation preprocessing part 121 generates aninterpolation division point of chopping with reference to thereciprocating central point (contour control point) from various valuesregarding the chopping operation to be passed, and temporarily saves thegenerated data in an interpolation data buffer 123 dedicated forchopping, as shown in FIG. 4(a).

Also, the contour control interpolation controlling part 122 generatesan interpolation division point of contour control from various valuesof contour control, and temporarily saves the generated data in aninterpolation data buffer 124 dedicated for contour control, as shown inFIG. 4(b).

The data saved in the interpolation data buffer 123 dedicated forchopping and the interpolation data buffer 124 dedicated for contourcontrol are called in sequence by the next contour control processingpart 13. A buffer area the contents of which are used as data isemployed as a new data saving area for following generated data.

The axial control processing part 13 has the three internal processingportions, including the acceleration/deceleration controlling part 130,the error correction controlling part 131 and the axial controlling part132.

The acceleration/deceleration controlling part 130, in the case ofchopping control, performs acceleration/deceleration processing forswitching the direction of reciprocating chopping operation as shown inFIG. 5(a), using data saved in the interpolation data buffer 123dedicated for chopping. In the case of contour control, theacceleration/deceleration controlling part 130 performsacceleration/deceleration processing based on the contour controlmovement start, end and moving shape as shown in FIG. 5(b), using datasaved in the interpolation data buffer 124 dedicated for contourcontrol.

Also, the error correction controlling part 131 corrects for a delay ofservo control remarkably appearing at a command position in the case ofthe fast reciprocating operation such as chopping operation, in which anerror amount is calculated for each of a plurality of axes controlled asthe oblique chopping operation, as shown in FIG. 7. Moreover, thecalculated error amount for each axis is synthesized as shown in FIG.8(a). This resultant error amount is decomposed into a chopping errorcomponent amount and a contour control error component amount, using achopping interpolation vector and a contour interpolation vector asshown in FIG. 8(b). This decomposed chopping error component amount andcontour control error component amount are convoluted on the nextoblique chopping command to make the error correction (by correct thenext oblique chopping command using the chopping error component amountand the contour control error component amount). Consequently, the errorcorrection is made as shown in FIG. 9.

This error correction is made using the error amounts at multiple timestemporarily saved in the NC internal memory, as shown in FIG. 9.

The axial controlling part 132 convolutes the interpolation data forchopping operation and contour control on the chopping interpolationdata and the contour interpolation data that are processed by theacceleration/deceleration controlling part 130, and the chopping errorcorrection amount calculated by the error correction controlling part131, as shown in FIG. 6(a). And the axial interpolation data for eachcontrol axis is generated from the convoluted interpolation data asshown in FIG. 6(b), in which each interpolation data is output to eachservo amplifier 19 to enable the machine tool to make the choppingcontrol operation.

Also, when the processing program analysis processing part 5 reads thechopping stop command (GΔΔ), the chopping control is stopped, and thecontour control is only made.

Accordingly, the chopping control is effected only with the control axessuch as the X axis and Y axis originally possessed without adding thechopping dedicated axis to the machine tool in this embodiment 1.

Also, the chopping control is enabled along with the contour control.

In this embodiment 1, to assist an understanding of the invention, thechopping operation is made with two control axes, but may be employedwith three or more control axes.

Embodiment 2

In the embodiment 1, various data for controlling the oblique choppingoperation, such as G . . . R . . . A . . . F . . . P . . . Q . . . , arecommanded from the processing program. However, various data such as R .. . A . . . F . . . P . . . Q . . . may be set and saved as theparameters in the set data holding memory 18 prepared for the numericalcontrol apparatus, but not commanded from the processing program.

In this case, if a chopping operation initiation command of G . . .alone is commanded to the processing program, the processing programanalysis processing part 5 reads and analyzes this G . . . , thechopping control is made using various data saved in the set dataholding memory 18.

Embodiment 3

In the previous embodiments, the chopping control initiation command andthe stop command are issued from the processing program. However, theoblique chopping start and stop commands may be issued directly to theinterpolation processing part 12 via the ladder processing part 9, thePLC interface 8 and the machine process controlling part 10 by turningon or off a specific external bit signal based on an outside signalinput from the input/output controlling part 11 or by the laddercircuit.

In this case, various data for controlling the oblique choppingoperation are set and saved as the parameters in the set data holdingmemory 18 prepared for the numerical control apparatus, whereby thechopping control is made using various data saved in the set dataholding memory 18, when a chopping initiation command is input into theinterpolation processing part 12.

INDUSTRIAL APPLICABILITY

As described above, the numerical control apparatus according to thisinvention is suitably employed for the control of the tool machinemaking the chopping control process.

1. A numerical control apparatus for making the contour control bycontrolling two or more control axes, characterized by comprisingchopping movement data generating means for generating the movement datafor making the chopping operation by controlling said two or morecontrol axes at the same time.
 2. A numerical control apparatus formaking the contour control by controlling two or more control axes,characterized by comprising chopping movement data generating means forgenerating the movement data for making the chopping operation bycontrolling said two or more control axes at the same time while makingthe contour control.
 3. The numerical control apparatus according toclaim 2, characterized in that said chopping movement data generatingmeans generates the movement data for making the chopping operation forsaid control axes at the same time while making the contour control insuch a manner as to convolute the movement data for making the choppingoperation and the movement data for making the contour control, anddistribute said convoluted data to each of said control axes.
 4. Thenumerical control apparatus according to claim 2 or 3, characterized byfurther comprising correction means for correcting a servo delay of eachcontrol axis to make the chopping operation at the same time whilemaking the contour control.
 5. The numerical control apparatus accordingto claim 4, characterized in that said correction means corrects a servodelay of each of two or more control axes to make the chopping operationat the same time while making the contour control in such a manner as toacquire a servo delay amount of each control axis by comparing theactual position feedback information for each control axis making thechopping operation at the same time while making the contour controlwith a command value, synthesize said acquired servo delay amount ofeach control axis, and distribute said synthesized servo delay amount toa chopping interpolation vector and a contour control interpolationvector.
 6. The numerical control apparatus according to claim 1 or 2,characterized in that a chopping operation initiation command and achopping operation stop command are issued from any one of a processingprogram and a ladder portion.
 7. The numerical control apparatusaccording to claim 1 or 2, characterized in that various data regardingthe chopping operation command are set as the parameters in a memory,and when the chopping operation initiation command is issued, thechopping control is performed using various data regarding the choppingoperation command set as said parameters.